This application claims priority to German Patent Application 19959598 filed on Dec, 10, 1999.
This invention relates to a process for the manufacture of a blade/vane of a turbomachine, in particular a gas-turbine engine, said blade/vane consisting of a metallic enveloping structure and a supporting structure made of a composite material which is provided inside the enveloping structure and is suitably joined to the enveloping structure. For background art, reference is made to DE 196 27 860 C1 and, in particular, to U.S. Pat. No. 3,699,623.
Composite materials or composites, i.e. in particular fibrous composite materials with polymeric and metallic matrix, find widest use for the manufacture of technical components. The main reason for their use is normally the favorable weight-to strength ratio. However, the surface characteristics of the composite material frequently do not satisfy the given requirements, which necessitates application of a metallic protective coating, for example, to the surface of the component made of such composite material. Since the material and physical properties of this protective coating and of the composite material frequently differ widely, the joint between the two elements of the component, the interface, is a weak point of this compound construction.
The aforementioned Specification U.S. Pat. No. 3,699,623 teaches a manufacturing process according to the generic part of claim 1, in which a metallic enveloping structure made of titanium is applied around a supporting structure made of a metallic-fiber reinforced composite material. A diffusion couple is thus formed between the enveloping structure and the supporting structure. Apparently, this manufacturing process is only suitable for metallic-matrix composite material and, in the long term, provides only an insufficiently stable bond between the enveloping structure and the so-called supporting structure.
The aforementioned Specification DE 196 27 860 C1 teaches a further manufacturing process according to the generic part of claim 1, in which a metal-felt weave made of metallic fibers or filaments is applied on the surface of a supporting structure made of a fiber-reinforced plastic and is bonded to the plastic structure with the same resin binding agent. The mechanical, virtually positive joint thus achievable is intended to increase the mechanical strength of the surface of the blade/vane made under this process; however, this process fails to provide a continuous surface which thus also lacks homogenous properties.
Summarizing, no process is presently known which enables a highly stressable joint to be made between a metallic skin or the enveloping structure, respectively, which provides for both corrosive and mechanical protection, and a supporting structure in a composite material in the inside of the enveloping structure. In a broad aspect, the present invention provides a solution to the above problematic.
It is a particular object the present invention to provide for this solution in that a metal felt weave is welded or soldered/brazed to a metal sheet which forms the enveloping structure, whereupon this sheet-felt-assembly is shaped to the blade/vane enveloping structure by hydro-forming or internal high-pressure forming, and in that the composite material which makes up the supporting structure is subsequently introduced into the cavity of the enveloping structure. Further objects and advantages of this invention become apparent from the subclaims, in particular a preferred blade/vane of a turbomachine manufactured under the process according to this invention.